It's a pretty basic expectation from most Hollywood movies that the heroes will eventually triumph over the villains, because that's what sends audiences home happy and makes them recommend films to their friends.
Most of the time, anyway.
But sometimes filmmakers have other ideas, and prefer to hand a rare W to the bad guys, concluding with an ending that categorically has the villains come out on top.
Though the sci-fi genre is largely built on the idea of humanity overcoming an exterior terrifying force, sometimes that's not the case at all, and whatever the protagonist is facing off against is eventually revealed to be insurmountable.
Perhaps it's an invading alien race, a secret society that's thousands of years old, a malevolent android, or an artificial intelligence with designs of world domination.
Whatever they are, these 10 movie villains all defeated the hero in one way or another, as left audiences the world over picking their jaws up off the floor.
These endings typically didn't make for the most uplifting viewing for those craving disposable, crowd-pleasing entertainment, but they certainly landed with bruising, unforgettable impact for the most part...
10. The Pod People - Invasion Of The Body Snatchers (1978)
The climax of 1978's Invasion of the Body Snatchers remake is a downer ending for the ages, brilliantly revising the more hopeful ending of the 1957 original for something much bleaker.
The film's final scene shows the Pods' industrious subversion of the United States in full swing, with survivors Matthew Bennell (Donald Sutherland) and his friend Nancy Bellicec (Nancy Cartwright) secretly meeting while attempting to avoid detection by the Pod People.
But as they meet up, Matthew suddenly raises a finger at Nancy and opens his mouth, letting out a disturbingly not-human scream, confirming that he's also been turned into a Pod Person.
Though we don't see what comes next, the implication is crystal clear, that Nancy will be turned next, and with the Pods being shown moving their operation to nearby cities on the West Coast, there's virtually nothing standing in the way of their total victory.
Considering that everybody needs to sleep - and that's when the Pod People get you - it's simply a matter of time before not only the entire U.S. but the whole globe succumbs to them.